Method of making piston rings



Nov. 9, 1937. R. s. NEWTON 2,093,790

METHOD OF MAKING PISTON RINGS Filed Jan. 22, 19:4 2 Shets-Sheet 1 H62. Mk1) INVENTOR Nov. 9, 1937. R. s. NEWTON 2,093,790

METHOD OF MAKING PiSTON RINGS Filed Jan. 22, 1934 2 Sheets-Sheet 2 INVENTOR Patented Nov. 9, 1937 UNlTED STATES PATENT OFFICE METHOD OF MAKING PISTON RINGS Application January 22, 1934, Serial No. 707,675

6 Claims.

This invention relates to an improved method of making piston rings by which extreme accuracy in the diameter of the finished ring and uniformity in the gap and overlap is brought about without the necessity of accurate machining or grinding of the ring surface.

Heretofore it has been the common practice in the manufacture of piston rings to turn or grind the outer surface of a cylinder, from which the rings were cut, to a given diameter with the accuracy desired in the final product. In the course of splitting the rings a predetermined amount was taken from each. Accurate grinding of the cylinder is expensive to the point of being prohibitive in large scale production. For this reason dependence is usually placed upon a variation in the gap at the overlapped ends to account for differences in the original diameters of rings. This means that only those rings which are of maximum diameter, originally, will have a full overlap when first put into use. Rings which originally have a minimum diameter, within the limits of accuracy permissible in quantity production, will have a considerable gap at the overlapped ends. This, of course, reduces the amount of expansion that can be permitted to offset wear and therefore reduces the average life of the rings. Y

According to the present invention the diameters of a large number of rings may be made uniform with such accuracy that a substantially fixed, maximum, amount of overlap may be provided for all. This is accomplished, furthermore without increasing the accuracy of thediameter of the cylinders from which the rings are produced. In fact less accuracy than heretofore required may be permitted. Toward the end mentioned the invention contemplates the removal of a variable amount from each ring, when it is split, sufficient to bring its outside diameter to a predetermined measurement with a full overlap.

Other objects and advantages of the invention will appear from the detailed description which will now be given in conjunction with the accompanying drawings in which:

Figure 1 is a schematic view showing the relation of, the ring and cutter following completion of the first operation.

Figure 2 is a side elevation of the parts shown in Figure 1, a portion being in section along the line 2-2 of Figure 1.

Figure 3 is a view similar to Figure 1 showing the parts after completion of the second operation.

Figure 4 is a perspective view on an enlarged scale showing the overlapping portions of one type of ring made in accordance with the .invention, and

Figure 5 is a similar view of a modified form of ring.

It will be understood that in the production of rings in accordance with this invention a complete, unbroken annulus is first produced in any convenient way, as by cutting a ring from the end of a cylinder formed of appropriate material. This ring is formed of the desired thickness to fit the grooves of the piston. It is preferably square or otherwise rectangular in cross-section. Now for the first operation, illustrated in Figure 1, the ring In is placed upon a suitable table or support with portions engaging shoulders ll formed by undercut formations in a pair of retaining blocks i2. Another portion at one side of the ring is positioned against a guide or stop l3. The blocks l2 are preferably arranged to be clamped to the table to firmly hold the intermediate portion. Extensions It may suitably be engaged over the ring for this purpose.

The ring is now ready for the first cutting operation by means of a two part cutter having a saw portion i5 and a milling portion i6 carried by a hub I l secured to a shaft l8. With the cutter and ring disposed in the angular relation illustrated in Figures 1 and 2, relative movement is produced between them in a horizontal direction, 1. e. parallel with the lower edge of the drawings. This serves to carry the saw portion of the cutter completely through the ring while the milling portion simply forms a substantially flat surface It diagonally across the ring from the outer edge 20 to one-face 2!. The arrangement is preferably such that portions of the surfaces 20 and 2| remain at the ends of the surface Hi. This surface extends from a shoulder 22 to the end of the ring. Upon completion of the cutting operation just described the ring and cutter are restored to the relative positions shown in Figures 1 and 2.-

The blocks l2 may now be loosened and the ring removed. A second ring may then be applied to the table in the same way and the operation repeated. Any desired number of rings may be subjected to th s first operation one after another. If the production at a. small plant simply warrants the installation of one machine for performing two operations upon a group of rings the machine may be suitably modified, after the entire group has been subjected to the-first operation, to prepare for the second operation. When production permits the installation of two or more machines the second operation may be performed upon a different machine and the same set-up may be maintained continuously on the two machines, so long as rings of a given size and form are being produced.

Referring now to Figure 3 the arrangement for the second operation is clearly illustrated.

.from which the rings are originally cut.

2 2,01 enoo The ring is placed upon a table inclined ,at an angle to the horizontal equal to that illustrated in Figure 2 but in the opposite direction, 1. e., inclined upwardly away from the cutter. A pair of clamping blocks 28, which may be the same as the blocks i2, is provided to clamp the ends of the ring firmly during the secondcutting operation. Beneath one of the clampingblocks the table is provided with a guide pin .24 projecting upwardly toward the portion 2' that extends over the ring. This pin is adaptedto engage the shoulder 22, formed in the ring during the first operation, and, in this way,- definitely positions the corresponding end of the ring. At three points, spaced 90 apart around the ring, there is preferably provided three guide blocks 20, 21 and 2| for definitely confining the outer.

contour of the ring. If desired one of these blocks might be omitted and the spacing of the others modified but the number and arrangement shown is considered preferable. Obviously other means might be provided for holding the outer contour of the ring in a definite, predetermined position. Y

when the ring is properly clamped as shown in Figure 3, relative movement is produced between the table and cutter just as for the first operation. The saw portion 29 of the cutter will remove any excess section of the ring beyond the predetermined circumference desired. At the same time the cutter portion 80 willmill a surface ll complementary to the surface I! at the other end of the ring. It will be apparent that in this way rings of uniform circumference, and hence uniform diameter when fully overlapped, will be produced even though considerable variation may exist. in the diameters of the cylinders The variation in the rings will depend entirely upon the accuracy with which the saw 20 operates in trimming the end of the split ring. This, obviously, can be performed with considerable accuracy without diiliculty.

The cooperating ends of the ring may be If the surfaces are curved, on the other hand,

the cutter I. must have slightly concave cutting edges while the cutter ll must have slightly convex cutting edges complemental to those of cutter It. If desired the surfaces at the ends of the ring may be in a plane inclined at a slight angle toward the end of the ring. This is illustrated. in Figure 5 wherein the surface 32 is inclined slightly so that the cross-section through the lapping portion or leg of the ring decreases slightly in area toward the free end. In a similar way the lapping portion 33 has its cooperating face inclined slightly so as to make the two ends complements] when they are fully. overlapped.

This angular relation of the surfaces can be produced by forming the cutting edges of the cutters I and 3| at a smallv angle to the axes ofthe cutters or by simply inclining the cutter axes slightly with relation to the horiaontakthe teeth of portions I. and II thenheing made parallel with the axes. The end surfaces '34 atthe point of split would, in the latter case, be'angled slightly to a true radial plane on account of the tilting of the sawblades but this would not be objectionable.

While the invention has been described in considerable detail in relation to a particular type of ring it will be understood that the improved method is applicable to the production of other types of rings as well. Various changes may be made-in the procedure ,to' suit special 'circum stances without departing from the general principle-and scope of the invention.

What I claim is: 1. A methodof making a lap joint piston ring which comprises splitting an unbroken ring,

forming aleg at one side only of the splitbya milling operation, then removing a portion of the ring at the opposite side only of the-split,

2. A- method of making a lap joint piston ring which comprises splitting an unbroken ring, si-

multaneously forming a leg at one side only of the. split by a cutting operation distinct from-said splitting operation, then removing a portion of thering at the opposite side only of the split, and simultaneously forming a leg mmplementary to the first mentioned leg at the end left by the removal of said portion. I

3. A method of making a lap joint piston ring which comprises forming an unbroken ring of slightly larger circumference than the desiredproduct, splitting the ring, removing aportion from the end of 'the ring at one side only of the split to reduce the ring to desired size, and forming complementary legsat the free ends of the ring by cutting operations distinct from said splitting and removing operations.

4 A method ofmaking a lap joint piston ring which comprises forming-an. unbroken ring of slightly larger circumference than the desired product, splitting the ring, confining the ring to a predetermined contour, removing a portion from the end .of the ring at one side only of the split to provide a ring of predetermined circumference, and milling complementary legs at the free ends of the ring.

5. A method of-making a lap 'joint piston ring which comprises forming an unbroken ring of slightly larger circumference than the desired 'product, splitting the ring, simultaneously milling the end of the ring at one side only of the split to form a leg, then removing the excess beyond a predetermined circumference from the opposite end only of the ring, and simultaneously milling the end left by the removal of said excess to provide a leg complementary to the first mentioned leg.

6. A method of making-a piston ring which comprises forming an unbroken 'ring'of slightly larger circumference than the desired product, sawing through the ring to split it, simultaneously milling a surface at anangle to the axis I of the ring at one side only ofthe split, retaining thesplit ring-at a definite predetermined circum-v ference, removing a section from the ring at' the opposite side only of the split, and simultane- 

